title: Electron-pinned defect-dipoles for high-performance colossal permittivity materials.
abstract: The immense potential of colossal permittivity (CP) materials for use in modern microelectronics as well as for high-energy-density storage applications has propelled much recent research and development. Despite the discovery of several new classes of CP materials, the development of such materials with the required high performance is still a highly challenging task. Here, we propose a new electron-pinned, defect-dipole route to ideal CP behaviour, where hopping electrons are localized by designated lattice defect states to generate giant defect-dipoles and result in high-performance CP materials. We present a concrete example, (Nb+In) co-doped TiO₂ rutile, that exhibits a largely temperature- and frequency-independent colossal permittivity (> 10(4)) as well as a low dielectric loss (mostly < 0.05) over a very broad temperature range from 80 to 450 K. A systematic defect analysis coupled with density functional theory modelling suggests that 'triangular' In₂(3+)Vo(••)Ti(3+) and 'diamond' shaped Nb₂(5+)Ti(3+)A(Ti) (A = Ti(3+)/In(3+)/Ti(4+)) defect complexes are strongly correlated, giving rise to large defect-dipole clusters containing highly localized electrons that are together responsible for the excellent CP properties observed in co-doped TiO₂. This combined experimental and theoretical work opens up a promising feasible route to the systematic development of new high-performance CP materials via defect engineering.
authors.affiliation: Research School of Chemistry, The Australian National University, Australian Capital Territory 0200, Australia.
authors.forename: Wanbiao
authors.initials: W
authors.lastname: Hu
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Ray L
authors.initials: RL
authors.lastname: Withers
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Frankcombe
authors.forename: Lasse
authors.initials: L
authors.lastname: Norén
authors.forename: Amanda
authors.initials: A
authors.lastname: Snashall
authors.forename: Melanie
authors.initials: M
authors.lastname: Kitchin
authors.forename: Paul
authors.initials: P
authors.lastname: Smith
authors.forename: Bill
authors.initials: B
authors.lastname: Gong
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
authors.forename: Jason
authors.initials: J
authors.lastname: Schiemer
authors.forename: Frank
authors.initials: F
authors.lastname: Brink
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wong-Leung
mesh_terms: D004553:Electric Conductivity; D007204:Indium / Q000737:chemistry; D008422:Materials Testing; D008962:Models, Theoretical; D013696:Temperature; D014025:Titanium; D014961:X-Ray Diffraction
chemical_list: D007204:Indium; C009495:titanium dioxide; D014025:Titanium